Is there anything I can do to prevent my one year old from sliding his chest clip down on his car seat?

I have checked to make sure it’s in the proper position and that it’s tight enough. I literally cannot get it anymore tighter without possibly hurting him. He can STILL slide his clip down and get his arms out and try to stand up! 😩

Does anyone have any advice? He is 16 months old. He can figure out how to escape almost everything. Crib, high chair, playpen. Now his car seat. 😭

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